# CVE-2026-72253: netfilter: nf_conntrack_sip: validate skb_dst() before accessing it

> A null pointer dereference in the Linux kernel SIP conntrack helper can cause a crash when external media is enabled on specific network subsystems.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** BELL-CVE-2026-72253, DEBIAN-CVE-2026-72253, GHSA-7j9w-2xg9-r3v4, UBUNTU-CVE-2026-72253

## What is CVE-2026-72253?

CVE-2026-72253 is a high-severity vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nf_conntrack_sip: validate skb_dst() before accessing it

tc ingress and openvswitch do not guarantee routing information to be
available. These subsystems use the conntrack helper infrastructure, and
the SIP helper relies on the skb_dst() to be present if
sip_external_media is set to 1 (which is disabled by default as a module
parameter).

This effectively disables the sip_external_media toggle for these
subsystems without resulting in a crash.

## Which versions are affected by CVE-2026-72253?


## How do I fix CVE-2026-72253?

Apply the vendor's patch.

## Is CVE-2026-72253 being exploited?

There is no known exploitation of CVE-2026-72253 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72253 and fix it if it is affected.

What it is: CVE-2026-72253 is a high-severity vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-72253 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-72253/ (Markdown: https://insights.sbomify.com/CVE-2026-72253/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72253
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72253
- OSV: https://osv.dev/vulnerability/CVE-2026-72253

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72253/
Summaries are generated and may contain mistakes; the official description above is the record.